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For further information, see CMDT Part 33-03: Pneumococcal Infections

Key Features

Essentials of Diagnosis

  • Fever, headache, altered mental status

  • Meningismus

  • Gram-positive diplococci on Gram stain of cerebrospinal fluid; counterimmunoelectrophoresis may be positive in partially treated cases

General Considerations

  • Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults and the second most common cause of meningitis in children > age 6 years

  • Head trauma, with cerebrospinal fluid leaks, sinusitis, and pneumonia may precede it

  • Penicillin-resistant strains may cause meningitis

Clinical Findings

Symptoms and Signs

  • Rapid onset, with fever, headache, meningismus, and altered mentation

  • Pneumonia may be present

  • Compared with meningitis caused by the meningococcus

    • Pneumococcal meningitis lacks a rash

    • Obtundation, focal neurologic deficits, and cranial nerve palsies are more prominent features and may lead to long-term sequelae

Differential Diagnosis

  • Meningitis due to other causes (eg, meningococcus, Listeria, aseptic)

  • Subarachnoid hemorrhage

  • Encephalitis

  • "Neighborhood reaction" causing abnormal cerebrospinal fluid, such as

    • Brain abscess

    • Epidural abscess

    • Vertebral osteomyelitis

    • Mastoiditis

    • Sinusitis

    • Brain tumor

  • Dural sinus thrombosis

  • Noninfectious meningeal irritation

    • Carcinomatous meningitis

    • Sarcoidosis

    • Systemic lupus erythematosus

    • Drugs (eg, nonsteroidal anti-inflammatory drugs, trimethoprim-sulfamethoxazole)

    • Pneumonia

    • Shigellosis


Laboratory Tests

  • See Table 30–1

  • Cerebrospinal fluid

    • Typically has > 1000 white blood cells/mcL (1 × 109/L), over 60% of which are polymorphonuclear leukocytes

    • Glucose concentration is < 40 mg/dL (< 2.22 mmol/L), or < 50% of the simultaneous serum concentration

    • Protein usually exceeds 150 mg/dL (1500 mg/L)

    • Gram stain shows gram-positive cocci in up to 80–90% of cases

  • In untreated cases, blood or cerebrospinal fluid cultures are almost always positive

  • Blood cultures are positive in 50% of cases

  • Urine antigen tests may be positive but are not sufficiently sensitive to exclude the diagnosis

Table 30–1.Typical cerebrospinal fluid findings in various CNS diseases (listed in alphabetical order after Normal).

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